Voltage stability is a major concern for power transmission in electrical power systems. Voltage stability is the ability of a power system to remain in a state of equilibrium under normal operating conditions and to regain an acceptable state of equilibrium after a load change, a generation capacity change, or other disturbances. The lack of voltage stability is believed to be a result of the power system attempting to restore power consumption beyond the capacity of the combined transmission and generation facilities. If not promptly corrected, the lack of voltage stability may lead to unacceptably low voltages (commonly referred to as a voltage collapse) in at least a part of the power system. A Voltage collapse can cause electrical equipment failures, blackouts, and other electrical system incidents.